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R&R 910 Open Face Cast - Mold Cracking
Posted: Tue Aug 26, 2003 2:32 am
by coolntn
OK, I've tried removing all water and chemically adhered water from my molds that are made from the R&R 910 material.
Has anyone had any problem with mold cracking ? These are minor and could be considered an 'embellishment'.....but I don't like 'em if I can get rid of them.
I noticed a cracked was developing around 1200 when I peeked in...that was before it even got up to 1550. Strange ?
I know there are options of mixing your own stuff, but I like the premixed if I can get it to work for me.
Any ideas or suggestions for my next go 'round would be great
Thanks,
Russ
More Info
Posted: Tue Aug 26, 2003 2:35 am
by coolntn
A little more info...its a small open face mold...the piece measure about 3 x 2 x .5 inches. With about 1.5 inches of mold thickness all around, top and bottom.
Hope that helps a little more.
Thanks again,
Russ
Posted: Tue Aug 26, 2003 3:41 pm
by lizpage
There has been a lot of discussion about mold cracking here.
My theory is that the molds crack either from stress- i. e. not strong enough molds to hold the glass (which does not sound like yours) -OR- that the molds are not dry when you fire them. You may want to thoroughly dry your mold in the kiln at 200 degrees for a couple of hours. Good Luck!
Drying...the ticket !
Posted: Wed Sep 03, 2003 12:52 pm
by coolntn
Ok, for those interested and having similar issues .... I more thoroughly read the instructions from the R&R910 webpage for using their investment.
It instructs a couple differnet temps to heat at (if I recall correctly), but I decided to go ahead and heat at 400 degrees F and hold for 2 hours. Did my pate de verre stuff and when I started the actually firing, I again held at 1 hour at 225 and then at 400 for another hour and then continued as normal at that point. I EXPERIENCED VERY VERY MINIMAL HAIRLINE CRACKS. Turned out good and I am happy
I will try next time, to just dry the mold out at 400 for 3 or 4 hours and see what happens, do the pate-de-verre and ramp up from there normally.
Thanks for the info !!!
Russ
Re: More Info
Posted: Sat Sep 06, 2003 12:40 pm
by charlie holden
coolntn wrote:A little more info...its a small open face mold...the piece measure about 3 x 2 x .5 inches. With about 1.5 inches of mold thickness all around, top and bottom.
Hope that helps a little more.
Thanks again,
Russ
This size piece of glass doesn't need 1.5 inches of mold around it. You could probbably get away with .5 inch. That would make drying easier and shorter. You might also add something to make the mold porous, like chopped newspaper or cellulose. (R&R may already have something like this in it for all I know. I don't use it.)
ch